1. Field of the Invention
The present invention relates to improvements in polishing discs and the method of making them, and in particular to a polishing disc cut from sheet abrasive material and adhered to an inexpensively produced plastic hub that locks onto a rotatable arbor.
2. Description of the Prior Art
In the field of dentistry it is necessary to contour, finish and polish restorative dental materials once they have been placed into or onto a tooth so that the restorative materials blend to the contour of the tooth with a smooth transition between the material and tooth structure. It is imperative that the restorative materials be highly polished to prevent plaque build up which leads to other complications.
The most common dental restorative materials currently used are composite, amalgam, gold, ceramics, acrylic, and glassionomers. These as well as other polishable materials usually require polishing with a minimum of at least two steps of sequential grits, with most materials requiring three to six steps before achieving satisfactory results. This series of polishings usually requires single-use, disposable discs having a sequence of grit sizes. For this reason, not only must dental polishing discs be inexpensive in terms of material and manufacturability, but to save dentists"" time they must also be capable of being very quickly secured to and removed from a driving arbor. Because the dental polishing discs is used inside a patient""s mouth, it must be relatively small, and be rigidly secured to the arbor so it won""t wobble or fly off.
Several prior art devices are available for this purpose. Generally they are comprised of grit coated thin discs of paper or plastic or thin rigid discs of abrasive, having a central aperture to receive a screw, pin, shaft or the like, by means of which the disc can be secured to a rotary drive shaft or arbor. With most prior art, the head of the shaft or arbor protrudes from the forward face of the dental polishing disc and clamps to the inner area of the disc by means of a metal or plastic eyelet that may be swaged through the disc. The protrusion of the shaft or arbor beyond the dental polishing disc limits the working area of the disc, and during polishing can inadvertently cause damage to the restorative material, tooth structure, or tissue.
U.S. Pat. Nos. 3,858,368 and 4,447,208 disclose a dental polishing disc in which the central hub or the entire polishing head is made of soft rubber. The central hub of such dental polishing discs are formed with a blind, hollow, cylindrically-shaped interior cavity having at least one flattened surface so a head portion of the arbor may be inserted into the cavity thus securing the disc to the arbor. The central hubs of these molded dental polishing discs can either be molded integrally with the polishing disc or molded separately and attached to the disc by means of an adhesive material. Because these dental polishing discs have a blind interior cavity the arbor cannot protrude beyond the dental polishing disc. Thus, dental polishing discs having molded rubber hubs prevent inadvertently damaging restorative material, tooth structure, or tissue. However, the molded central hub or entire polishing head is comparatively expensive, bulky, and can be manufactured only in a limited range of shapes and sizes. Using a blind hole configuration as in these devices, there always exists a rubber filled space between the disc and the arbor which remains flexible thus permitting the dental polishing disc to wobble on the arbor. Furthermore, due to poor engagement between the molded rubber hub and the arbor such dental polishing discs tend to fly off the arbor when polishing with the surface of the disc adjacent to the arbor.
A primary object of the present invention is to provide a rotary polishing disc and hub which is inexpensive and easy to manufacture.
Another object of the present invention is to provide a polishing disc and hub which attach quickly, easily, and removably to the arbor with a rigid secure fit without wobble and without the danger of falling off.
A related object of the present invention is to form the hub using an inexpensive plastic extrusion.
Another object of the preferred embodiment of the present invention is provide a hub having an interior surface along the entire length of which matches the cross-sectional shape of the arbor insertable thereinto thus providing a tight friction fit to retain the polishing head securely on the arbor free from wobbling.
Another corollary object of the preferred embodiment of the present invention is to prevent the polishing head from flying off of the arbor.
A related object of an alternate embodiment of the present invention is to provide a hub having several flexible arms which engage an interior surface of a mating, hollow arbor.
Another object of the present invention is to adhere the hub to the back face of the abrasive polishing disc so the entire front abrasive surface of the polishing disc is usable for polishing.
One more object of the present invention is to improve engagement between the hub and larger diameter or high-friction dental polishing discs cut from sheet abrasive material.
Briefly, in one aspect the present invention is a rotary polishing disc adapted for attachment to an end of a rotatable arbor. The rotary polishing disc includes a disc-shaped piece of sheet material having an abrasive material on at least one surface thereof. The rotary polishing disc also includes a hub that is juxtaposed with and fixed to the disc-shaped piece of sheet material. The hub has a longitudinal axis that is oriented substantially perpendicular to a surface of the disc-shaped piece of sheet material with which the hub is juxtaposed.
In one embodiment of this aspect of the present invention the hub is cylindrically-shaped with the longitudinal axis extending through a hollow interior of the hub. The hollow interior of this hub is formed with a cross-sectional shape that is adapted to mate with and to receive a projecting end of the rotatable arbor completely thereinto so the projecting end becomes juxtaposed with the disc-shaped piece of sheet material.
In another embodiment of this aspect of the present invention, the hub is elongated with a first end that is juxtaposed with and fixed to the surface of the disc-shaped piece of sheet material. This second embodiment of the hub also has a second end that projects away from the disc-shaped piece of sheet material. The second end of this hub is pierced by a slot to establish at least one flexible arm that has an outwardly projecting tip at the end thereof furthest from the disc-shaped piece of sheet material. For this second embodiment of the hub, the flexible arm and tip are shaped to enter into, mate with and engage an interior surface of a socketed end of the rotatable arbor.
To fix the disc-shaped piece of sheet material more securely to the hub, the disc-shaped piece of sheet material of either of the preceding embodiments may be pierced by a central aperture through which passes a retainer plug. The retainer plug has a flat cap formed at an end thereof which is juxtaposed with a surface of the disc-shaped piece of sheet material furthest from the hub. For the first embodiment of the hub described above, a second end of the retainer plug, furthest from the flat cap, enters into and becomes frictionally engaged with the hollow interior of the hub. For the second embodiment of the hub described above, the second end of the retainer plug enters into and becomes frictionally engaged with a cavity formed into the first end of the hub adjacent to the central aperture.
In another aspect, the present invention includes a improved arbor which, in a first configuration, has a projecting end that is adapted to receive and mate with a hollow interior surface of a hub of a rotary polishing disc. This first improved arbor configuration includes a barb protruding from an exterior surface of the arbor that is adapted to spear the hub when the hollow interior of the hub is disposed on the arbor. A second improved arbor configuration includes a hollow socket formed at one end of the arbor. The hollow socket has an interior surface which is shaped to receive and to mate with the flexible arm and tip at one end of an elongated hub.
An advantage of the present invention is simpler manufacturing and lower manufacturing cost for enhanced performance dental polishing discs.
The intended use for the present invention is dental grinding and polishing discs. Accordingly, the present invention will be specifically described with reference to that field by way of illustration. However, the present invention is not limited to use in that field, and appears useful in other applications that require a small rotary polishing disc. These and other features, objects and advantages will be understood or apparent to those of ordinary skill in the art from the following detailed description of the preferred embodiment as illustrated in the various drawing figures.